Abstract : A number of investigations were performed on Mg/Mg(C1O4)2/m-DNB A-size and D-size organic depolarized primary cells. Formulation studies showed that the cathodic wetness level and the type of carbon black employed have a significant effect upon cell performance. Best overall cell service is obtained with cells employing a cathodic mix incorporating a high surface area specialty carbon black at a moderate wetness level. The use of the maximum tolerable wetness level resulted in highest initial cell services, but had a detrimental effect upon shelf life with use of one of the specialty carbon blacks evaluated. Information is presented on the background and the current status of the specialty carbon black required for use in the organic depolarized primary battery system. (Author)